Most prior processes for decontaminating soils have concentrated their efforts on removing the contaminants from the vadose zone above the aquifer. Such processes are seen in U.S. Pat. Nos. 4,593,760; 4,660,639; and 4,730,672; and involve injection of air into the vadose zone to urge the contaminants toward a withdrawal well.
A process for removing contaminants from the aquifer itself is shown in U.S. Pat. No. 4,183,407 and in pending patent application Ser. No. 151,065, filed Feb. 1, 1988 now U.S. Pat. No. 4,809,673. The process disclosed in the pending application teaches the injection of atmospheric air into the aquifer to urge the contaminant out of the aquifer and into the vadose zone toward the withdrawal well. This process is commonly referred to as sparging. One major drawback to sparging is the stimulation of bacterial growth or the formation of ignorganic precipitates in the aquifer saturated zone or by injection of oxygen thereinto.